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/*
* anytun
*
* The secure anycast tunneling protocol (satp) defines a protocol used
* for communication between any combination of unicast and anycast
* tunnel endpoints. It has less protocol overhead than IPSec in Tunnel
* mode and allows tunneling of every ETHER TYPE protocol (e.g.
* ethernet, ip, arp ...). satp directly includes cryptography and
* message authentication based on the methodes used by SRTP. It is
* intended to deliver a generic, scaleable and secure solution for
* tunneling and relaying of packets of any protocol.
*
*
* Copyright (C) 2007 anytun.org <satp@wirdorange.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program (see the file COPYING included with this
* distribution); if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "log.h"
#include "keyDerivation.h"
#include "mpi.h"
#include "threadUtils.hpp"
#include <stdexcept>
#include <iostream>
#include <string>
#include <gcrypt.h>
void KeyDerivation::init(Buffer key, Buffer salt)
{
Lock lock(mutex_);
gcry_error_t err;
// TODO: hardcoded cipher-type and keysize??
err = gcry_cipher_open( &cipher_, GCRY_CIPHER_AES128, GCRY_CIPHER_MODE_CTR, 0 );
if( err ) {
cLog.msg(Log::PRIO_ERR) << "KeyDerivation::init: Failed to open cipher: " << gpg_strerror( err );
return;
}
master_salt_ = SyncBuffer(salt);
master_key_ = SyncBuffer(key);
updateMasterKey();
}
void KeyDerivation::updateMasterKey()
{
gcry_error_t err;
err = gcry_cipher_setkey( cipher_, master_key_.getBuf(), master_key_.getLength() );
if( err )
cLog.msg(Log::PRIO_ERR) << "KeyDerivation::updateMasterKey: Failed to set cipher key: " << gpg_strerror( err );
}
KeyDerivation::~KeyDerivation()
{
Lock lock(mutex_);
gcry_cipher_close( cipher_ );
}
void KeyDerivation::setLogKDRate(const uint8_t log_rate)
{
Lock lock(mutex_);
if( log_rate < 49 )
ld_kdr_ = log_rate;
}
void KeyDerivation::generate(satp_prf_label label, seq_nr_t seq_nr, Buffer& key)
{
Lock lock(mutex_);
gcry_error_t err = gcry_cipher_reset( cipher_ );
if( err )
cLog.msg(Log::PRIO_ERR) << "KeyDerivation::generate: Failed to reset cipher: " << gpg_strerror( err );
// see at: http://tools.ietf.org/html/rfc3711#section-4.3
// * Let r = index DIV key_derivation_rate (with DIV as defined above).
// * Let key_id = <label> || r.
// * Let x = key_id XOR master_salt, where key_id and master_salt are
// aligned so that their least significant bits agree (right-
// alignment).
//
Mpi r(48); // ld(kdr) <= 48
if( ld_kdr_ == -1 ) // means key_derivation_rate = 0
r = 0; // TODO: no new key should be generated if r == 0, except it is the first time
else
{
Mpi seq(32);
seq = seq_nr;
Mpi rate(48);
rate = 1;
rate = rate.mul2exp(ld_kdr_);
r = seq / rate;
}
// TODO: generate key only if index % r == 0, except it is the first time
Mpi key_id(128); // TODO: hardcoded size
Mpi l(128); // TODO: hardcoded size
l = label;
key_id = l.mul2exp(48) + r;
Mpi salt(master_salt_.getBuf(), master_salt_.getLength());
Mpi x(128); // TODO: hardcoded size
x = key_id ^ salt;
u_int32_t written;
u_int8_t *ctr_buf = x.mul2exp(16).getNewBuf(&written); // TODO: hardcoded size
err = gcry_cipher_setctr( cipher_ , ctr_buf, written );
delete[] ctr_buf;
if( err )
cLog.msg(Log::PRIO_ERR) << "KeyDerivation::generate: Failed to set CTR: " << gpg_strerror( err );
for(u_int32_t i=0; i < key.getLength(); ++i) key[i] = 0;
err = gcry_cipher_encrypt( cipher_, key, key.getLength(), NULL, 0);
if( err )
cLog.msg(Log::PRIO_ERR) << "KeyDerivation::generate: Failed to generate cipher bitstream: " << gpg_strerror( err );
}
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